The Structure and Dynamics of Agricultural Landscapes as Drivers of Biodiversity - Landscape Ecology for Sustainable Environment and Culture - page 279

Table 14.1 Quantity of semi
natural areas in each
landscape unit

Landscape unit (a) (b) (c)

Woodland and fallow land (%) 15 11 7

Permanent grassland (%) 30 20 18

Hedgerow density (m/ha) 79 63 45

spans. These were two families of diptera: Chironomidae, and Empididae, cara-
bidae, herbs, breeding passerines, woody plants and small mammals. All these
groups have been sampled using specific sampling methods. Birds were counted
according to ''IPA'' method (Blondel et al. 1970 ), small mammals were studied by
using the pellets of the Barn owl (Tyto alba), carabids were caught with inter-
ception traps, diptera with yellow attractive traps and plants were identified in
hedgerows, with 3014 relevés for woody plants and 455 relevés for herbs.
The results are presented in Table 14.2 . They show that the different groups
react differently to the changes in landscape structure. Diptera only decrease as
semi natural areas decrease, there are few changes but not consistent with the
landscape structure gradient for carabids breeding passerines and herbs, and no or
almost no differences for woody plants and small mammals. When looking at
community similarity between units (a) and (c) Burel et al. ( 1998 ) showed that
three classes of taxonomic groups could be identified. First, communities of dip-
tera Empididae and Chironomidae lose species from unit (a) to unit (c). For
Empididae, species with small wings and a low power of dispersal are not present
in landscapes where the distance between water courses and the closest hedgerows,
two elements needed to accomplish their life cycle, is high as in unit (c) (Morvan,
N. unpublished data). Second, communities of carabidae and herbs do not vary that
much in species richness but there is a shift in species composition, some are only
present in the site with a high proportion of semi natural areas, while others are
only present where this proportion is low. Large apterous carabid forest species
characterize unit (a) with a high quantity of semi natural areas, while smaller
winged species, adapted to disturbances characterize unit (c) with a high propor-
tion of crops (Aviron et al. 2005 ). Third, communities of breeding passerines and
small mammals have almost the same species in all the units. For small mammals
Millan-Pena et al. ( 2003 ) showed that if the species were the same their relative
abundance varied. Forest species such as the bank vole (Clethrionomys glareolus)

Table 14.2 Species richness

Unit (a) Unit (b) Unit (c)

Dipera chironomidae 28 29 15

Diptera empididae 84 82 56

Carabid beetles 55 51 50

Breeding birds 40 35 38

Small mammals 11 11 11

Herbs 189 132 171

Woody plants 40 41 39